At present, most of the mainstream permanent magnet brushless motors use surface-mounted or embedded magnetic tiles to form a ring-shaped magnetic circuit. However, the splicing magnetic ring has the disadvantages of high processing precision of magnetic tiles, high assembly difficulty, poor stability of magnetic pole transition, and serious motor noise, and the structure requires a frame structure of soft magnetic materials to fix the magnetic tiles, and the loss of magnetic flux is obvious, which has a great impact Motor power factor and efficiency.
The radiation magnetic ring is a kind of ring-shaped permanent magnet with a special orientation. It is magnetized radially around the magnetic ring. It can be widely used in the fields of servo motors, magnetic transmission, magnetic bearings, and sensors instead of spliced magnetic rings.
Key benefits of radiating magnetic loops include:
1. The radiation ring is an integral magnetic ring, the dimensional accuracy is better controlled, and the assembly process is simplified;
2. The surface field is sinusoidal, and evenly distributed, and the transition zone between magnetic poles is small, so the motor runs stably and the noise is low;
3. The magnetization method and magnetic field distribution are various, and the magnetic circuit design is more flexible.
Radiation magnetic rings can be divided into magnetic field orientation and pressure-oriented magnetic rings according to the orientation method. Among them, sintered or bonded magnetic rings are mostly magnetic field-oriented, and hot-pressed/heat-deformed magnetic rings are mostly pressure-oriented. According to the material, it can be divided into: ferrite permanent magnet ring, rare earth permanent magnet ring, and other permanent magnet rings, among which the rare earth permanent magnet ring mainly includes samarium cobalt permanent magnet ring and neodymium iron boron permanent magnet ring, and the highest magnetic performance is sintered or Hot-pressed/heat-deformed NdFeB magnetic ring. According to the shape, the inner and outer diameter ratio is less than 0.7 in a thick-walled ring, and the inner and outer diameter ratio is greater than 0.9 in a thin-walled ring.
Due to the relatively mature bonding process and low price, the output of bonded NdFeB radiation rings accounts for the largest proportion. However, the density and performance of the bonded magnetic ring are low, and high-end application scenarios are limited. However, for high-performance sintered and hot-pressed/hot-deformed NdFeB magnetic rings, there is a large difference in the shrinkage ratio and thermal expansion coefficient between the easy magnetization axis and the hard magnetization axis of the NdFeB grains, so in the preparation, magnetization and The assembly process is extremely fragile, the yield is low, and the price is generally high. Japan carried out the development of radiation ring equipment and technology earlier, and its equipment accuracy and stability, as well as product grades, have great advantages. The research on radiation rings in China started relatively late, but at present, many enterprises and scientific research institutes have been able to stably supply radiation ring products of various sizes and grades.